How to use Dichlor to bring up CYA

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H

hurst_b

0
May 24, 2015
8
Wichita/Kansas
I just opened my pool and want to start the SLAMMING process. I have a very low CYA level (around 0 ppm). I am at 0 on FC (algae pool).
I have Dichlor on hand (left over from the "bad old days") so would like to use it to get the FC up to 10 ppm and the CYA up to 30 ppm.
Can someone help me with the Pool Math? How much Dichlor should i add? At what point to i retest the CYA? Once i am at 30 ppm on the CYA, i plan to switch back to bleach for my chlorine source. Thanks.
 
Welcome to TFP!

In 13,000 gallons it takes 2 lbs of dichlor to raise the FC level by 10. That will also raise CYA by 9. So you can raise the FC level by 10 three times and then you should retest the CYA level.
 
13,000 gallons of water.
99% Dichlor: 6.4 LBS will raise the CYA level from 0 to 30 ppm. Don't use any more than 6.4 LBS. 2 LBS of it will raise the FC level from 0 to 10 ppm. I think I would wait a few days before retesting the CYA level. You could use half (not all at once), then wait and retest, then put in more just to make sure you don't overshoot it.
 
Thanks for the help. I found another thread that points to the bottom of the Pool Math page, "effects of adding chemicals". I guess i could have answered my own question if i had found that first. I added 3 doses of 99% dichlor at 35 oz by volume. I then switched to 10% bleach assuming the dichlor raised my CYA to 33ppm. I've read on this forum that it takes a "few" days for the CYA level to register. How long should i wait to retest the CYA?
 
i retested the CYA level today and found i was at 60ppm. Not sure how i went from zero to 60. Can someone help with with the how many ounces by volume is equal to one pound of dichlor? Second question, on the pool math calculator at the bottom, "effects of adding chemicals", when you enter in ounces and dichlor is that ounces by volume or ounces by weight? Thanks in advance.
 
The effects of adding chemicals section always uses oz by weight for solids.

Conversions between weight and volume are always approximate, as different brands are somewhat different densities.

When adding CYA with dichlor, you only need an hour with the pump running before you are ready to have it show up on the test.
 
1 LB of 99% Dichlor (16oz weight) = 15 oz by volume.
As you can see if you measured by volume you wouldn't have overshot it by double. Not sure what happened there. Did you just open the pool and test the CYA without circulating the water first?

I'm not sure if Pool Math is weight or volume but its close enough for both.

A CYA level of 60 ppm isn't much to worry about really. I wouldn't add any more though. Just keep your FC in the proper range for that CYA level.
Pool School - Chlorine / CYA Chart
 
Thanks for the help, guys. I did the CYA test first thing when i opened the pool before circulating the water. i am guessing that was a mistake? Should i have circulated it for an hour and then tested it? I'm guessing i was at 30ppm from the beginning instead of zero. This is my second year of using this trouble free pool method so i am still making one mistake after the next, but i'm learning thanks to your help.
 
I always circulate the water before I test. Even when opening.

The same thing happened to me a few years ago when I opened the pool. I usually open late. Before I came here I was using test strips and it showed 0'ish. After I circulated the water it showed 50'ish. Granted test strips are not accurate but they are not that inconsistant. I guess maybe the CYA tends to settle or something when the water sits still for months.
 
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